Field of the Invention
Preferred embodiment of the present application relates to the art of a selectable one-way clutch adapted to selectively enable torque transmission only in one direction and to interrupt torque transmission in both directions.
Discussion of the Related Art
A selectable one-way clutch is brought into engagement mode by bringing struts held on a pocket plate into engagement with notches formed in a notch plate, and into disengagement mode by rotating a selector plate interposed between the pocket plate and the notch plate in such a manner to push the struts into the pocket of the pocket plate. In the prior art, lubrication device for the selectable one-way clutch have been proposed to prevent malfunction caused by friction acting between the rotary plates.
For example, JP-A-2003-021220 describes a device for delivering oil between a notch plate and a stator. To this end, according to the teachings of JP-A-2003-021220, the stator is provided with a recess formed on a pocket of a stator body, and oil passages connected to the recess.
In the selectable one-way clutch, the pocket plate is fixed to a stationary member, and lubrication oil is applied between the rotary plates. However, the selector plate may be rotated undesirably by a rotation of the notch plate through the lubrication oil. Especially, such drag torque derived from a shearing force of the oil that is applied to the selector plate is increased with an increase in viscosity of the oil. For example, if a temperature of the oil is extremely low, viscosity of the oil is increased significantly. In this situation, the selector plate may be rotated by the drag torque resulting from rotating the notch plate, and as a result, an actuator arm may be actuated to bring the notch plate into engagement undesirably with the pocket plate. Such erroneous engagement of the selectable one-way clutch may be prevented by enhancing an elastic force of a return spring counteracting the drag torque. In this case, however, larger actuator for rotating the selector plate is required to overwhelm the enhanced spring force, and consequently the selectable one-way clutch is enlarged.